Scott and Sir Mick had been together for 13 years
L'Wren Scott, a designer and the girlfriend of Sir Mick Jagger, has been found dead in her New York City flat.
Scott, 49, was found at 10:00 local time (14:00 GMT) by her assistant.
Police are treating it as a suicide, although the medical examiner has yet to determine an official cause of death.
A spokesman for Sir Mick said the singer was "completely shocked and devastated" by Scott's death.
Scott, born Luann Bambrough, was raised by adoptive parents in the US state of Utah.
She began her career as a model in Paris, then moved to Los Angeles to become a fashion stylist, according to a biography on her company's website.
She and Sir Mick, the singer of the Rolling Stones, began dating in 2001.